Reaction of alcohols and cyclic carbonates, such as those of the above formula, to produce alkylcarbonates by transesterification in the presence of various catalysts is known in the art. For example, U.S. Pat. No. 3,896,090 discloses a process for preparing polycarbonates from carbon dioxide and 1,2-epoxides or from alkylene carbonates and a monomeric polyol in the presence of alkali metal borate, alkaline earth metal borate, ammonium borate, or hydrocarbyloxy titanate catalyst. Also, U.S. Pat. No. 4,691,041 teaches a process for the preparation of ethylene glycol and dimethylcarbonate by reacting methanol and ethylene carbonate in the presence of a series of heterogenous catalyst systems including ion exchange resins with tertiary amine, quaternary ammonium, sulfonic acid and carboxylic acid functional groups, alkali and alkaline earth silicates impregnated into silica and ammonium exchanged zeolites.
U.S. Pat. No. 4,181,676 discloses use of alkali metal and/or alkali metal compound catalyst for the preparation of a dialkylcarbonate by contacting a glycol carbonate with alcohol at an elevated temperature in the presence of less than 0.01 percent by weight of the alkali metal or alkali metal compound. A list of some conventional transesterification catalysts was published in U.S. Pat. No. 5,173,518, including tetraisopropyl orthotitanate, dibutyltin oxide, dibutyltin dilaurate and zirconium (IV) acetyl-acetonate, and alkali metal alkoxides, for example sodium methoxide, sodium ethoxide, and potassium ethoxide.
A list of catalysts for esterification or ester-interchange is shown in U.S. Pat. No. 4,891,421, including inorganic acids and organic acids; chlorides, oxides, and hydroxides of metals such as Li, Na, K, Rb, Ca, Mg, Sr, Zn, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Pd, Sn, Sb, and Pb; salts of the above-exemplified metals with fatty acids such as acetic acid, oxalic acid, octylic acid, laurie acid, and naphthenic acid; alcoholates such as sodium methylate, sodium ethylate, aluminum triisopropoxide, isopropyl titanate, n-butyl titanate, and octyl titanate; phenolates such as sodium phenolate; and organic metal compounds of metals such as Al, Ti, Zn, Sn, Zr, and Pb.
U.S. Pat. No. 4,062,884 discloses a process for the preparation of dialkylcarbonates by reacting an alcohol with a cyclic carbonate, wherein the reaction is carried out in the presence of an organic base catalyst, preferably a tertiary aliphatic amine.
Aluminum trifluoride catalyst is used in U.S. Pat. No. 5,252,771 in a process for the production of a diarylcarbonate useful in the preparation of polycarbonate molding resins comprising contacting an aromatic hydroxy compound and a carbonyl halide or aryl haloformate. The support for the aluminum trifluoride catalyst in this process includes refractory oxides, ceramics, or other inert materials such as silica, aluminosilicate, carbon, silicon carbide, aluminum nitride, titania, high silica ZSM-5, and zirconia.
Thallium is claimed as a catalyst in U.S. Pat. No. 4,434,105 for a process for preparing a dialkylcarbonate which comprises contacting an alkylene oxide with an aliphatic or cycloaliphatic alcohol and carbon dioxide at an elevated temperature. This patent lists various catalysts useful for such a conversion reaction including basic organic nitrogen compounds and oxides, hydroxides, and salts of alkali and alkaline earth metals. Solid supports are mentioned for the catalyst useful in the latter process such as magnesia and alumina.
Dialkylcarbonates can be prepared in a continuous manner by transesterification of ethylene carbonate or propylene carbonate with alcohols in the presence of a catalyst in a column equipped with packing or baffles in U.S. Pat. No. 5,231,212 by passing the reactants in countercurrent such that the ethylene carbonate or propylene carbonate is metered into the upper part of the column, the alcohol is metered into the lower part of the column, and the catalyst is arranged as a fixed bed in the column or is also metered into the upper part of the column in solution or suspension. A variety of catalysts are taught for use in the patent process, including hydrides, oxides, hydroxides, alcoholates, amides, or salts of alkali metals, preferably lithium, sodium, and potassium. Thallium compounds, nitrogen-containing bases, heterogeneous catalysts, complexes or salts of tin, titanium, or zirconium, and bifunctional organic catalysts are also suggested for the patent process.
U.S. Pat. No. 5,235,087 discloses manufacture of dialkylcarbonates by reacting carbon monoxide with alkyl nitrites over a modified platinum metal-supported catalyst at an elevated temperature in a continuous gas phase reaction, the reaction being carried out with the exclusion of additional oxidizing substances and, optionally, the presence of a lower alcohol.
In a similar vein, U.S. Pat. No. 5,283,351 discloses a process for producing an organic carbonate which comprises reacting an organic hydroxy compound and carbon monoxide in the absence of oxygen and in the presence of a catalyst comprising (a) palladium or a palladium compound, (b) a quinone or an aromatic diol formed by reduction of the quinone or a mixture thereof, and (c) a halogenated onium compound. The palladium component may be deposited on carbon, alumina, silica, silica-alumina, or zeolite.
Cyclic amidine catalyst is disclosed for a process for the transesterification of carbonate esters and carboxylic acid esters at elevated temperatures in U.S. Pat. No. 4,652,667. The amidine catalyst can be homogeneous or heterogeneous. In the heterogeneous catalyst, the amidine compound is chemically bonded to an inert support through the bonding of the surface atoms of the support to one or more of the free valences of the amidine group. Suitable supports include organic supports such as polymer resins, e.g., polystyrene, polystyrene/divinyl benzene copolymer, polyacrylate, and polypropylene; or inorganic supports such as silica, alumina, silica-alumina, clay, zirconia, titania, hafnia, carbides, diatomaceous earth, and zeolites.